A413 Aluminum Alloy -The Pressure-Tight Die Casting Alloy

A413 is a near-eutectic aluminum-silicon alloy containing approximately 12% silicon -close to the aluminum-silicon eutectic composition of 12.6%. This single compositional fact defines everything that makes A413 different from A380 or ADC12 and explains why it is specified for hydraulic manifolds, pneumatic valve bodies, and any application where internal leakage is a functional failure rather than a cosmetic defect.

Understanding A413 requires understanding eutectic solidification. At the eutectic composition, a binary alloy transforms from liquid to solid at a single temperature rather than over a range, producing the finest possible microstructure -no coarse dendrites, minimal inter-dendritic shrinkage, and the lowest total volumetric contraction of any composition in the alloy system. A413's proximity to this point is the source of its pressure tightness.

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Chemical Composition

Element	Min %	Max %	Key Role
Silicon (Si)	11.0	13.0	Near-eutectic -finest microstructure, lowest shrinkage
Copper (Cu)	-	1.0	Kept low vs A380 -less intermetallic formation
Iron (Fe)	-	2.0	Reduces die soldering
Zinc (Zn)	-	0.50	-
Magnesium (Mg)	-	0.10	-
Manganese (Mn)	-	0.35	-
Nickel (Ni)	-	0.50	-
Tin (Sn)	-	0.15	-
Aluminum (Al)	Balance	-	Base metal

Per ASTM B85. Silicon content is the defining parameter -11-13% versus A380's 7.5-8.5%.

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Mechanical Properties (As-Cast HPDC)

Property	A413	A380 (reference)	Difference
Tensile strength	290 MPa (42,000 psi)	317 MPa	-%
Yield strength	145 MPa (21,000 psi)	159 MPa	-%
Elongation	2.5%	3.5%	-
Hardness	80 HRB	80 HRB	Same
Shear strength	172 MPa	190 MPa	-%
Fatigue strength (5x10^8	130 MPa	138 MPa	-%

A413's mechanical properties are slightly lower than A380 across the board. This is the direct trade-off for its superior pressure tightness and casting soundness -the near-eutectic microstructure that minimizes porosity also produces slightly lower strength. For pressure vessel and sealing applications, this trade-off is always worthwhile: a leaking manifold at 350 MPa tensile is useless; a sound manifold at 290 MPa does its job reliably.

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Physical Properties

Property	A413	A380
Density	2.66 g/cm³	2.71 g/cm³
Thermal conductivity	121 W/m·K	96 W/m·K
Electrical conductivity	31% IACS	27% IACS
Coefficient of thermal expansion	20.0 μm/m·°C	21.1 μm/m·°C
Melting range (near-eutectic)	574-596°C	540-595°C
Casting temperature	600-660°C	620-680°C
Modulus of elasticity	69 GPa	71 GPa
Poisson's ratio	0.33	0.33

A413's thermal conductivity of 121 W/m·K is 26% higher than A380's 96 W/m·K -the highest of the standard aluminum die casting alloys. This makes A413 valuable not only for hydraulic applications but also for thermal management components where maximum heat dissipation matters.

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Why A413 Has Superior Pressure Tightness

The mechanism behind A413's pressure tightness is microstructural, and understanding it helps engineers make better material decisions.

The Eutectic Effect on Solidification

When aluminum-silicon alloys solidify, the sequence depends on silicon content relative to the eutectic point (12.6% Si):

Hypoeutectic alloys (A380, A360 at 8-10% Si): Solidification begins with primary aluminum dendrites forming from the melt. The spaces between dendrite arms are the last to solidify -and the most susceptible to shrinkage porosity. These inter-dendritic spaces, if they cannot be fed by liquid metal, become the voids that compromise pressure tightness.

Near-eutectic alloy (A413 at 12% Si): The near-eutectic composition dramatically suppresses primary dendrite formation. Solidification occurs more simultaneously throughout the casting volume, producing a finer, more uniform structure with narrower inter-dendritic channels. The total volumetric shrinkage is lower, and the remaining shrinkage is distributed as finer, more dispersed pores rather than the larger, more interconnected voids of hypoeutectic alloys.

The practical result: A413 HPDC castings show ASTM E505 Class 2- porosity as standard. A380 HPDC castings in equivalent geometry show Class 3-. For a hydraulic manifold, the difference between Class 2 and Class 4 porosity can mean the difference between passing and failing a 200 bar leak test.

Vacuum-Assisted Casting Takes A413 to Another Level

When VADC (vacuum-assisted die casting) is combined with A413, the results approach gravity cast or LPDC quality in terms of internal soundness. KastMfg's VADC + A413 programs regularly achieve ASTM E505 Class 1 porosity -the highest quality designation -enabling parts to pass helium mass spectrometry leak tests (<10^-7 mbar·L/s) without post-cast impregnation.

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Hydraulic Performance Data

KastMfg has pressure-qualified A413 manifolds and valve bodies to the following levels across production programs:

Casting Type	Alloy	Process	Burst Pressure Achieved	Rated Working Pressure
Directional valve body	A413	Standard HPDC	280-320 bar	70-80 bar
Directional valve body	A413	VADC	360-420 bar	90-105 bar
Hydraulic manifold block	A413	VADC	350-400 bar	85-100 bar
Filter housing	A413	Standard HPDC	200-250 bar	50-52 bar
Accumulator end cap	A413	VADC	500+ bar	125+ bar

All figures from production qualification records. Actual performance depends on part geometry, wall thickness, and test protocol.

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Thermal Conductivity Applications

A413's 121 W/m·K thermal conductivity -the highest of the aluminum die casting alloys -makes it valuable beyond hydraulic applications:

High-power heat sinks: Where A360 (113 W/m·K) is the typical thermal management alloy, A413 (121 W/m·K) provides an additional 7% improvement. For high-power density applications (IGBT modules, power converters, fast-charging EV equipment), this difference reduces junction temperatures by 3-°C under typical operating conditions.

Liquid-cooled manifolds: EV battery thermal management manifolds and liquid-cooled power electronics housings benefit from A413's combined pressure tightness (for the cooling circuit) and thermal conductivity (for heat transfer to the coolant).

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A413 vs A380 -When to Specify A413

Requirement	A413	A380
Internal pressure > 100 bar working	Required	Marginal
Helium leak test < 10^-6 mbar·L/s	Required (with VADC)	Not achievable
T6 heat treatment (vacuum cast)	Possible	Marginal
Maximum thermal conductivity	Better (121 vs 96 W/m·K)	Standard
Maximum tensile strength	Weaker (290 vs 317 MPa)	Better
Machinability	Good	Excellent
Cost premium vs A380	~3-%	Baseline

For applications where pressure tightness is not a requirement, A380 is the better choice -higher strength, better machinability, lower cost. A413 is specified precisely and only when pressure tightness is a design requirement.

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Applications

Fluid Power -Primary Market

• Hydraulic directional control valve bodies (D03, D05, D08 ISO patterns)
• Hydraulic manifold blocks (mono-block, sectional, custom)
• Hydraulic pump and motor port blocks
• Pneumatic valve bodies requiring pressure integrity
• Accumulator shell halves and end caps
• Filter head bodies and bypass valve housings
• Pressure regulator and relief valve bodies

Thermal Management

• High-power LED heat sink housings
• Power electronics cold plates and heat spreaders
• EV battery thermal management manifold bodies
• Inverter and onboard charger housings (combined thermal + pressure tightness)
• Industrial drive enclosures with internal cooling circuits

Medical and Instrumentation

• Analytical equipment fluid manifolds
• Medical gas manifold housings
• Pressure vessel components for laboratory equipment

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Testing and Quality for A413 Programs

KastMfg's standard qualification for A413 hydraulic programs:

1. Alloy verification: OES spectrometer analysis of every melt to ASTM B85 A413 limits. Silicon content is the primary control parameter -deviation outside 11.0-13.0% affects both casting behavior and pressure performance.

2. Process monitoring: Injection velocity (target: filling complete in <150 ms), peak pressure, intensification pressure, and die temperature logged every shot. VADC programs additionally log vacuum level at injection trigger.

3. X-ray inspection: Radiographic inspection per ASTM E505. Acceptance class per customer specification (typically Class 1- for hydraulic applications). Defective parts identified and removed before pressure test.

4. Pressure testing: 100% air decay or nitrogen pressure test at 1.5x rated working pressure. Hold time and decay limit per customer specification. Helium leak testing available for ultra-low leak rate requirements. Records archived per part serial number.

5. First article inspection: Full CMM dimensional layout on all features. Port face flatness, bore cylindricity, and thread form gauging documented in the FAI package.

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Impregnation as an Alternative to VADC

For programs where VADC is not required for structural or T6 reasons but pressure tightness is marginal with standard HPDC, vacuum pressure impregnation (VPI) provides a cost-effective path to reliable sealing:

VPI draws a methacrylate resin into open pore networks under vacuum, then cures it under pressure. The sealed porosity can no longer form a leak path. VPI-treated A413 castings reliably pass 80-150 bar air decay tests in production.

KastMfg coordinates VPI through a qualified partner. Impregnated parts are supplied with impregnation batch certificates. This approach is standard for programs producing 10,000-100,000 pieces per year where the cost of dedicated VADC tooling is not justified.

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Equivalent Designations

Standard	Designation
ASTM B85 (USA)	A413.0
EN 1706 (Europe)	EN AC-47000
JIS H5302 (Japan)	ADC1
BS 1490 (UK)	LM20 (approximate)

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Frequently Asked Questions

Why is A413 less machinable than A380?

The high silicon content (12%) in A413 produces a microstructure with a continuous network of eutectic silicon particles throughout the matrix. Silicon is hard (~1,000 HV) and abrasive, causing accelerated cutting tool wear in drilling, boring, and milling operations compared to A380. KastMfg uses silicon carbide-compatible carbide grades and PCD (polycrystalline diamond) tooling on high-volume A413 programs to maintain tool life and bore quality.

Can A413 be electroplated or anodized?

A413 can be anodized, but the high silicon content produces a darker, less uniform anodized layer than lower-silicon alloys. Type II anodizing on A413 is functional (corrosion protection) but not suitable for decorative applications. For decorative anodizing, A360 or wrought alloys are preferred. Chrome or nickel plating is not practical on A413 for the same reason -zinc die casting is the preferred substrate for decorative electroplating.

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A413 hydraulic casting inquiry: yaoqingpu1983@gmail.com | +86 138 1403 4409 | No.6, Rungu Road, Nanjing, China